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PICU Intranet

Intra-abdominal pressure monitoring

  • Note: This guideline is currently under review.


    Measurement of intra-abdominal pressure is used to identify children at risk of intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS).  IAH & ACS are most likely to occur in the setting of major fluid resuscitation, severe gut oedema, intra-peritoneal or retroperitoneal bleeding, or ascites.  Patient groups may include trauma, burns, septic shock, post abdominal surgery.  IAH & ACS can cause significant morbidity and mortality due to reduced venous return and cardiac output, and altered respiratory mechanics. This results in end organ dysfunction; renal failure, impaired hepatic blood flow, respiratory failure, poor splanchnic perfusion and increased intracranial pressure are potential problems. Early recognition and treatment of IAH & ACS has been shown to significantly improve morbidity and mortality.


    The aim of this guideline is to outline the management principles related to intra-abdominal pressure monitoring within the Paediatric Intensive Care Unit at the Royal Children's Hospital.

    Definition of terms

    Bladder Pressure: reflects the intra-abdominal pressure and is measured via the indwelling urinary catheter. It is expressed in mmHg.

    Intra-abdominal Pressure (IAP): is the pressure within the abdominal cavity. 

    • Normal IAP in a well child is 0 mmHg and in a child on positive pressure ventilation is 1 - 8 mmHg.
    • IAP in critically ill children is approximately 4-10mmHg

    Intra-abdominal hypertension (IAH): is defined as a sustained or repeated pathological elevation of IAP greater than 10 mmHg.11 

    • Grade I: IAP 12-15mmHg
    • Grade II: IAP 16-20 mmHg
    • Grade III: IAP 21-25 mmHg
    • Grade IV: IAP >25mmHg

    Abdominal compartment syndrome (ACS): is defined as sustained IAP greater than 10 mmHg, with or without abdominal perfusion pressure less than 60mmHg13 and the onset of new or worsening organ failure directly attributed to elevated IAP. The syndrome is associated with 90%-100% mortality if not recognised and treated in a timely manner. 11 

    Abdominal perfusion pressure (APP):  APP = Mean Arterial Pressure (MAP) – IAP. In adults keeping this greater than 50-60mmHg significantly improves morbidity & mortality. The appropriate APP for children is unknown, but will be less than the adult level due to a lower MAP.

    Primary IAH or ACS: is a condition associated with injury or disease in the abdominopelvic region that frequently requires early surgical or interventional radiological intervention

    Secondary IAH or ACS: refers to conditions that do not originate from the abdominopelvic region

    Assessment of risk factors for elevated Intra-abdominal pressure

    • Diminished abdominal wall compliance
      • Major trauma & burns; acute respiratory failure; abdominal surgery
    • Increased intra-luminal contents
      • Gastroparesis; ileus; pseudo-obstruction
    • Increased abdominal contents
      • Ascites/liver dysfunction; Haemoperitioneum/pneumoperitoneum;
    • Capillary leak/fluid resuscitation
      • Acidosis (pH<7.2); hypotension; hypothermia (under 33 degrees C); massive fluid resuscitation; poly transfusion; coagulopathy; sepsis, major trauma & burns.  


    IAP can be measured directly or indirectly.

    • Direct measurement is obtained via a needle or catheter in the peritoneal space, and IAP is measured using a fluid column or pressure transducer system. This is the most accurate method but associated with side effects such as bowel perforation and peritonitis.
    • IAP is usually measured indirectly via the patient's bladder.  The changes in intravesical pressure demonstrate an accurate reflection of intra-abdominal pressure (IAP)
    • Patients with two or more risk factors for IAH should have a baseline IAP performed and if elevated should have continued serial measurements
    • IAP is measured 4 hourly or more frequently if IAP greater than 12mmHg or the patient is hypotensive, has decreased urine output or a tense abdomen
    • An increased IAP reading should be rechecked to ensure there is not a technical problem e.g. a blocked catheter
    • If IAP greater than 12mmHg then medical management of IAH should be instituted in a timely manner to prevent further morbidity and mortality. Renal impairment can occur with IAP as low as 10-15mmHg.
    • Medical management will not be discussed in detail in this document but involves improving systemic perfusion, measures to reduce IAP, and in refractory cases early abdominal decompression. Excessive fluid administration should be avoided as it is strongly associated with ACS. The patient will need close clinical monitoring of organ function.

    Procedure for Intra-abdominal pressure monitoring

    Equipment required

    • Foley© urine catheter of appropriate size(this procedure assumes catheter has already been inserted into the patients bladder)
    • Urine bag for drainage of urine
    • 2 x 3 way tap
    • Connector (leur lock to catheter tip)
    • Pressure transducer and tubing
    • 50ml leur lock syringe
    • 10ml or 30ml leur lock syringe
    • Sterile 0.9% sodium chloride
    • Clamp

    Preparation of monitoring equipment

    1. Perform hand hygiene.
    2. Clean trolley / work surface with detergent and water or detergent disinfectant wipe
    3. Identify and collect all equipment for procedure
    4. Perform hand hygiene 
    5. Open procedure pack or tray by using external corners 
    6. Prepare patient and caregivers – use gloves when appropriate e.g. removing dressings or soiled nappy. Remove gloves if worn, perform hand hygiene and reapply new gloves
    7. Using an aseptic non touch technique, prime the transducer set and monitoring lines with sterile 0.9% sodium chloride only
    8. The tubing must be free of kinks and air bubbles.
    9. Connect drainage end of urinary Foley catheter (tip is already inserted in patients bladder) to the urine drainage bag with connector and two, 3-way taps. (see photo below).
    10. Attach pressure transducer to 3-way tap closest to the urinary catheter connector.
    11. Ensure all connections are securely luer locked.
    12. All transducer monitoring lines should be clearly labelled. 
    13. Urine flow into the drainage bag should be unclamped and uninterrupted except during IAP measurement. 
    14. Refer to invasive haemodynamic monitoring guideline for more information.


    Measurement of Intra-abdominal pressure

    1. Patient should be placed in the supine position for measurement. 
      - If this is not clinically feasible it is important to recognise that elevation of the head of the bed will result in a higher IAP. 
      - Document position and ensure all subsequent readings are taken in the same position.
      - At end of measurement return all patients to head up/reverse trendelburg position 15 degrees or greater to reduce risk of ventilator associated pneumonia (VAP).
    2. Adjust the height of the transducers so that the top of the 3 way tap (atmospheric port) is levelled at the cross section of the mid-axillary line and the iliac crest and zero the transducer. 
    3. Clamp the drainage tube to the urine bag
    4. Fill the bladder with 1mL/kg (minimum of 3 mL and maximum 25mLs) of 0.9% sterile sodium chloride using the syringe.  The volume of fluid in the bladder should be constant for each measurement.
    5. Close the stopcock of the syringe and allow 30 to 60seconds for equilibrium to occur. Obtain the mean pressure reading upon end expiration (this minimises the effects of pulmonary pressures).
    6. The abdominal blood flow should produce fluctuations in the waveform.  Factors that affect measurements

    • IAP increased with inspiration and decreases with expiration
    • Higher body mass index is correlated with higher IAP in adults but not children
    • Position of patient - have a higher IAP in prone and semi recumbent positions than when supine
    • Tense abdominal muscles
    • Volume of fluid instilled
    • Presence of air bubbles in the fluid column
    • Kinking of the monitoring lines
    • Position of the transducer

    Discontinuing monitoring

    • Monitoring of IAP can cease when IAP is less than 10 mmHg for several hours and the patient is clinically improving. The patient should continue to receive close clinical observation for deterioration
    • The transducer/monitoring attachments can be disconnected and removed prior to the removal of the patient's urinary catheter. Protecting key parts using an aseptic non touch technique.
    • Perform hand hygiene & don gloves
    • Using aseptic non-touch technique
    • Detach the transducer at the 3 way tap
    • Re-attach the end of urinary Foley catheter to the urinary drainage bag 
    • Remove gloves and perform hand hygiene, clean work surface / trolley 
    • Discard the transducer in the appropriate waste, perform hand hygiene. 

    Special considerations

    • 0.9% sodium chloride should only be used to fill the patient's bladder when undertaking an intra-abdominal pressure measurement.
    • The tubing must be free of kinks and air bubbles.
    • All transducer monitoring lines should be clearly labelled
    • Transducer sets should be changed weekly.
    • All connections should be securely luer locked.
    • All interventions must be carried out using an aseptic technique


    Infection of the bladder is a complication of this procedure. Symptoms vary depending on the age of the child but include:

    • Fever
    • Vomiting
    • General malaise
    • Frequency
    • Local pain
    • Dysuria

    Urine culture and sensitivity is the gold standard for diagnosis if an infection is suspected


    • Order the Intra-abdominal pressure monitoring, including frequency on EPIC
    • Document the IAP and APP in the patient's flowsheets on EPIC


    World Society of Abdominal Compartment Syndrome:

    Evidence table

    Click here to view the evidence table for this guideline. 


    1. Balough Z, Jones B, Amours S, Parr M and Sugrue M (2004) Continuous intra-abdominal pressure measurement technique.  The American Journal of Surgery Volume 188(6):679-684
    2. Cheatham M, Malbrain M, Kirkpatric A, Sugrue M, Parr M et al (2007). Results from the international conference of experts on intr-aabdominal hypertension and abdominal compartment syndrome. II Recommendations. Intensive Care Medicine. 33:951-962.
    3. Davis P, Koottayi S, Taylor A, Butt W. (2005) Comparison of indirect methods of measuring intra-abdominal pressure in children. Intensive Care Medicine. 31:471-475
    4. Ejike J, Bahjri K, Mathur M. (2008). What is the normal intra-abdominal pressure in critically ill children and how should we measure it? Critical Care Medicine. 36(7):2157-2162
    5. Ejike J, Kadry J, Bahjri K, Mathur M. (2010). Semi recumbent position and body mass percentiles: effects on intra-abdominal pressure measurements in critically ill children.
    6. Gallagher JJ (2000) Ask the Experts Critical Care Nurse, 20, 1 p: 87. 
    7. Iberti TJ, Lieber CE, Benjamin E. (1989) Determination on intra-abdominal pressure using a transurethral bladder catheter: clinical validation of the technique.  Anesthesiology, 70 (1): 47-50 
    8. Kirkpatrick A, Roberts D, Waele J, Jaeschke R, Malbrain M, et al (2013). Intra-abdominal hypertension and the abdominal compartment syndrome: updated consensus definitions and clinical practice guidelines from the World Society of the Abdominal Compartment Syndrome. Intensive Care Medicine 39:1190-1206
    9. LCP Rao, CR Chaudhry, LCS Kumar (2006) Abdominal Compartment Pressure Monitoring - a simple techniques. MJAFI,Vol. 62, No. 3.
    10. Newccombe, J., Mathur, M. & Ejike, J.(2012) Abdominal Compartment Syndrome in Children. American Association of Critical-Care Nurses, Dec; Vol. 32 (6), pp. 51-61; Publisher: 
    11. Ravishankar N, Hunter J (2005) Measurement of Intra-abdominal hypertension in intensive care units in the United Kingdom. British Journal of Anaesthesia Volume 94, Number 6 Pp. 763-766.
    12. Reitsma J, Schumacher B (2018) Nursing Assessment of intra-abdominal hypertension and abdominal compartment syndrome in the neonate. The National Association of Neonatal Nurses; Vol 18 (1): 7-13  
    13. Stafford, R. (2004, Revised 2008) Intra-Abdominal pressure monitoring. Publisher: Operative Techniques in General Surgery.
    14. Prasad G R, Subba Rao J V, Aziz A, Rashmi T M (2012) The role of routine measurement of intra-abdominal pressure in preventing abdominal compartment syndrome. J Indian Association of Paediatric Surgeons; Vol 22 (3):134-138
    15. Woolford, M. Skylas, K. (2014) Intra-abdominal Pressure Monitoring (IAP), CRG_PG2014_9088; Sydney Local health District

    Please remember to read the disclaimer


    The revision of this nursing guideline was coordinated by Jenny Raccanello and Kim Morris of PICU, and approved by the Nursing Clinical Effectiveness Committee. Updated January 2020.